Beamforming in a Wi-Fi network occurs during wireless data transfers between transmitters (i.e., a beamformer) and receivers (i.e., a beamformee) such as access points and stations. More specifically, rather than broadcasting a signal to a wide area to reach a target, beamforming concentrates the signal directly at the target that is faster, stronger, and has a longer range, with improved SNR (signal-to-noise ratio). Beamforming is enabled by transmitters and receivers that use MIMO (multiple-input, multiple-output) technology. Data is sent using multiple antennas to increase throughput and range with propagation over multiple paths.
Previous standards such as IEEE 802.11n (promulgated by the Institute of Electrical and Electronics Engineers) support beamforming capability, but without any specific direction on how it is to be implemented. Consequently, a router or access point may not be compatible with a station having a different implementation. Newer standards such as IEEE 802.11 ac and IEE 802.11 ac wave 2 provide particular protocols for beamforming as to how transmitters and receivers communicate with each other and provide information about their relative positions. This will increase the number of beamforming enabled products brought to market.
With the advent of MU-MIMO (multiple user MIMO), antennae can now transmit to multiple receivers at the same time rather than being limited to a single user at a time under SU-MIMO (single user MIMO). Multi user beamforming is significantly more time-dependent than single user and therefore can require up to date channel information as the spatial arrangement of multiple receivers changes.
However, beamforming measurements are very costly and will bring down throughput if not done accurately. One beamforming feedback for a single receiver could cost 0.5 to 1% of airtime. Receivers that constantly change locations need more beamforming measurements to prevent stale data. On the other hand, receivers that do not move or change locations infrequently waste computing and network resources with unnecessary beamforming measurements.
Because stations in IEEE 802.11 protocols select access points, a resulting configuration of stations for access points can have disparate beamforming requirements. In other words, one station can be relatively stationary and only require a single measurement while another station can be very mobile and require frequent measurements, while the transmitter is forced to also frequently measure the relatively stationary station when using MU-MIMO.
What is needed is a robust technique for optimizing beamforming with stations selectively grouped according to mobility profiles. Groups leverage the advantages of MU-MIMO while avoiding the higher resource overhead by selectively using SU-MIMO.